def test_pop_back(self):
dq = LinkedDeque(['A', 'B', 'C'])
assert dq.length() == 3
assert dq.front() == 'A'
dq.pop_back()
assert dq.length() == 2
assert dq.front() == 'A'
dq.pop_back()
assert dq.length() == 1
assert dq.front() == 'A'
assert dq.is_empty() == False
dq.pop_back()
assert dq.length() == 0
assert dq.front() == None
assert dq.is_empty() == True
def test_pop_back(self):
q = LinkedDeque()
with self.assertRaises(ValueError):
q.pop_back()
q.push_front("A")
assert q.length() == 1
assert q.pop_back() == "A"
assert q.is_empty() is True
q.push_back("two")
q.push_front("one")
assert q.pop_back() == "two"
assert q.pop_back() == "one"
with self.assertRaises(ValueError):
q.pop_back()
assert q.is_empty() is True